To abbreviate design time, the new drawings were based on the Sokol suit used on the Vostok missions. A prototype of the new suit, known as Sokol K1, was produced in 1971, with workshop drawings going through further revisions and refinements from August 1971 through March 1972. The suit was tested on the ground in 1972 and in space onboard Soyuz 12 in September 1973. From that point onward, the Sokol-K1 and its subsequent generations were used on all Soyuz flights for the launch, docking, and descent phases.
In an emergency the 10 kg suit could protect the wearer in open space. The suit included the 2AC-9000-0 pressure suit without the integral helmet, 2AC-9001-00 inner pressurized bladder, and 2AC-9009-00 soft helmet
The Sokol K1 ("Falcon") crew rescue suit of the 1970's was first worn aboard Soyuz 12 and continued in use until succeeded by the improved KV2 model flown in the Soyuz T-2 spacecraft on 5 June, 1980. It was worn by crews flying aboard Soyuz spacecraft during launch and descent. Each suit was connected to an on-board life support system in the capsule which supplied oxygen, electrical power, suit ventilation and water for the cooling garment worn underneath. The suit was designed to not impede the astronaut during flight in a pressurized cabin and to support the astronaut's life in case of cabin depressurization. The soft suit consisted of two layer enclosures, an outer restraint layer of white nylon canvas with royal blue trim, and an internal pressure bladder of rubber and rubberized material. The integral helmet had a soft hood and a hinged plastic visor. The K1 had lacing on the front opening of the suit (replaced by two zippers in the later model); a smaller helmet and visor than the later suits; and the pressure regulator was separate and located at the side on the suit. In case of cockpit depressurization, pure oxygen was supplied to the suit. The pressure regulator provided two suit pressure modes - 400 hPa (main mode) and 270 hPa (back-up).
Other external features of the suit were the blue anodized aluminum visor flange; trussed sleeves with adjustable articulating cables in the upper arm; webbed belt lashings; a pressure gauge on the left sleeve covered by a protective gasket; a mirror on an elasticized band on the right wrist; detachable gloves; a lace-up crotch with triangular packet; anodized aluminum umbilical inlets on the torso for electrical, air and coolant lines; the pressure equalization valve on the chest; a support sling running from chest to back by means of webbed belts and metal clips; adjustable webbed straps, marked in mm, attached to metal rings on the side seams and along the crotch; pleated knees; two utility pockets on each leg; and integral soled shoes.
The suit was developed in 1973-1979. It was designed to support a suited astronaut for up to 30 hours in a pressurized cabin and two hours in an unpressurized one. Ventilating air was provided at 150 l/minute and oxygen at 20 l/minute in pressurized operation.
Each suit was tailor-made to fit individual crew members. In the Soyuz spacecraft they reclined in Kazbek seats which had custom-fitted molded liners.
The wearer climbed into the suit via the laced front opening; the suit was then sealed by gathering folds of the space suit cloth and wrapping rubber bands around them. The suit was one-piece, including the helmet, but excluding the gloves which were put on separately.
The Sokol was not comfortable to walk around in due to its internal wiring and lack of ventilation (the wearers had to carry their own ventilator to avoid overheating). It was essentially designed to fit in the Kazbek seat, on one's back with the knees up. The helmet's soft cover was folded back when the wearer was upright; it could only fit over the head when lying in the seat.
After manufacture of a individually-tailored flight suit, the crew member occupied the Kazbek seat with the custom-fitted couch liner and sat in the flight posture under positive pressure for two hours. The suit was readjusted as a result of this first fit test. The same procedure was then repeated in a vacuum chamber, with simulation of oxygen supply to the suit helmet. Finally the suit fit was checked again at Baikonur prior to the mission, and the crew member would spend some time in the suit in the reentry capsule of the actual spacecraft that would take them to orbit. On the day of the flight, the final check was accomplished by Zvezda personnel during suiting up for the lift-off, and even then last-minute adjustments could be made.
During cosmonaut and crew training at the Gagarin Cosmonaut Training Center in Star City, the crew members also wore training versions of their suits during sessions in the Soyuz simulator, and in wilderness survival and ocean recovery training.
Zvezda ground support test equipment and fixtures were used in all preflight testing. The suits were ventilated with air supplied from cosmodrome ground sources during fit checks at Baikonur. Air conditioning was provided by this ground support equipment during fit checks. The suits were then connected to portable ventilation units for the trip to the spacecraft. These included a fan that brought ambient air to the suit, batteries for power, and cooling via a block of ice inserted prior to use. The same simple portable units had been used since Voshkod-2 in 1965.
Gross mass: 10 kg (22 lb).